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Date:      Wed, 12 Jul 2017 09:43:26 +0200
From:      Roman Divacky <rdivacky@freebsd.org>
To:        Ryan Libby <rlibby@FreeBSD.org>
Cc:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r320908 - head/sys/kern
Message-ID:  <20170712074326.GA41347@vlakno.cz>
In-Reply-To: <201707120730.v6C7UExf041447@repo.freebsd.org>
References:  <201707120730.v6C7UExf041447@repo.freebsd.org>

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Clang knows about %b modifier and can do some semantic analysis on it.
Currently it type checks the first arg to be an int and the second to be
a char*.

Do you think it would be worth modifying the checks to include
this new functionality? Do you think you would like to take a stab
at it? 

Search for FreeBSDbArg in contrib/llvm/tools/clang/lib/Sema/SemaChecking.cpp
if you want to take a look.

Thanks, Roman

On Wed, Jul 12, 2017 at 07:30:14AM +0000, Ryan Libby wrote:
> Author: rlibby
> Date: Wed Jul 12 07:30:14 2017
> New Revision: 320908
> URL: https://svnweb.freebsd.org/changeset/base/320908
> 
> Log:
>   kvprintf %b enhancements
>   
>   Make the %b formatter accept number formatting flags. It will now accept
>   alternate form, precision, and length modifiers. It also now partially
>   supports field width (but forces left justification).
>   
>   Reviewed by:	markj
>   Approved by:	markj (mentor)
>   Sponsored by:	Dell EMC Isilon
>   Differential Revision:	https://reviews.freebsd.org/D11284
> 
> Modified:
>   head/sys/kern/subr_prf.c
> 
> Modified: head/sys/kern/subr_prf.c
> ==============================================================================
> --- head/sys/kern/subr_prf.c	Wed Jul 12 07:26:07 2017	(r320907)
> +++ head/sys/kern/subr_prf.c	Wed Jul 12 07:30:14 2017	(r320908)
> @@ -650,7 +650,7 @@ kvprintf(char const *fmt, void (*func)(int, void*), vo
>  	uintmax_t num;
>  	int base, lflag, qflag, tmp, width, ladjust, sharpflag, neg, sign, dot;
>  	int cflag, hflag, jflag, tflag, zflag;
> -	int dwidth, upper;
> +	int bconv, dwidth, upper;
>  	char padc;
>  	int stop = 0, retval = 0;
>  
> @@ -676,7 +676,7 @@ kvprintf(char const *fmt, void (*func)(int, void*), vo
>  		}
>  		percent = fmt - 1;
>  		qflag = 0; lflag = 0; ladjust = 0; sharpflag = 0; neg = 0;
> -		sign = 0; dot = 0; dwidth = 0; upper = 0;
> +		sign = 0; dot = 0; bconv = 0; dwidth = 0; upper = 0;
>  		cflag = 0; hflag = 0; jflag = 0; tflag = 0; zflag = 0;
>  reswitch:	switch (ch = (u_char)*fmt++) {
>  		case '.':
> @@ -724,28 +724,9 @@ reswitch:	switch (ch = (u_char)*fmt++) {
>  				width = n;
>  			goto reswitch;
>  		case 'b':
> -			num = (u_int)va_arg(ap, int);
> -			p = va_arg(ap, char *);
> -			for (q = ksprintn(nbuf, num, *p++, NULL, 0); *q;)
> -				PCHAR(*q--);
> -
> -			if (num == 0)
> -				break;
> -
> -			for (tmp = 0; *p;) {
> -				n = *p++;
> -				if (num & (1 << (n - 1))) {
> -					PCHAR(tmp ? ',' : '<');
> -					for (; (n = *p) > ' '; ++p)
> -						PCHAR(n);
> -					tmp = 1;
> -				} else
> -					for (; *p > ' '; ++p)
> -						continue;
> -			}
> -			if (tmp)
> -				PCHAR('>');
> -			break;
> +			ladjust = 1;
> +			bconv = 1;
> +			goto handle_nosign;
>  		case 'c':
>  			width -= 1;
>  
> @@ -883,6 +864,10 @@ handle_nosign:
>  				num = (u_char)va_arg(ap, int);
>  			else
>  				num = va_arg(ap, u_int);
> +			if (bconv) {
> +				q = va_arg(ap, char *);
> +				base = *q++;
> +			}
>  			goto number;
>  handle_sign:
>  			if (jflag)
> @@ -939,6 +924,26 @@ number:
>  
>  			while (*p)
>  				PCHAR(*p--);
> +
> +			if (bconv && num != 0) {
> +				/* %b conversion flag format. */
> +				tmp = retval;
> +				while (*q) {
> +					n = *q++;
> +					if (num & (1 << (n - 1))) {
> +						PCHAR(retval != tmp ?
> +						    ',' : '<');
> +						for (; (n = *q) > ' '; ++q)
> +							PCHAR(n);
> +					} else
> +						for (; *q > ' '; ++q)
> +							continue;
> +				}
> +				if (retval != tmp) {
> +					PCHAR('>');
> +					width -= retval - tmp;
> +				}
> +			}
>  
>  			if (ladjust)
>  				while (width-- > 0)
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